回车和换行的历史

命名历史

在计算机还没有出现之前，有一种叫做电传打字机（Teletype Model 33）的玩意，每秒钟可以打10个字符。
但是它有一个问题，就是打完一行换行的时候，要用去0.2秒，正好可以打两个字符。
要是在这0.2秒里面，又有新的字符传过来，那么这个字符将丢失。
于是，研制人员想了个办法解决这个问题，就是在每行后面加两个表示结束的字符。一个叫做"回车"，告诉打字机把打印头定位在左边界；另一个叫做"换行"，告诉打字机把纸向下移一行。
这就是"换行"和"回车"的来历，从它们的英语名字上也可以看出一二。

"回车"（carriage return）和"换行"（line feed） 是来源机械英文打字机
"车"指的是纸车,带着纸一起左右移动的模块.
当开始打第一个字之前，要把纸车拉到最右边，上紧弹簧.随着打字，弹簧把纸车拉回去.每当打完一行后，纸车就完全收回去了.所以叫回车.
换行的概念就是:打字机左边有个"把手",往下扳动一下,纸会上移一行.

不同系统中的差异

后来，计算机发明了，这两个概念也就被般到了计算机上。
那时，存储器很贵，一些科学家认为在每行结尾加两个字符太浪费了，加一个就可以。
于是，就出现了分歧。

Unix系统: \n
Windows: \r\n
Mac: \r

引用文章

ChatGPT的回答

我：Why were carriage returns and line feeds created?

ChatGPT：Carriage returns and line feeds were created as a means of controlling how text was displayed on early computer systems and printers.

In the early days of computing, text was typically printed on teletype machines, which used a combination of mechanical and electrical systems to print characters on paper. These machines used a roll of paper that was fed through the machine, with characters being printed on the paper one at a time.

To control the position of the printing head, teletype machines used two separate control codes: a carriage return (CR) and a line feed (LF).

A carriage return (CR) code instructs the machine to move the printing head all the way to the left margin of the paper. This was necessary because the printing head would typically be positioned at the right side of the paper after printing a line of text, so a carriage return was necessary to reset the position of the head.

A line feed (LF) code instructs the machine to move the paper up by one line, so that the next line of text can be printed. This was necessary because the paper on a teletype machine was fed vertically through the machine, so moving the paper up by one line was necessary to print on the next line.

Today, carriage returns and line feeds are still used in some contexts, such as in programming languages or when working with text files in certain operating systems. However, the way they are used has evolved over time and varies depending on the specific context.

我：Why is the carriage return or line feed at the end of the text different in different operating systems?

ChatGPT：The reason why carriage return or line feed at the end of text is different in different operating systems is rooted in historical differences in how these operating systems handled text and line endings.

In Unix and Unix-like operating systems, such as Linux and macOS, a line feed (LF) character is used to mark the end of a line of text. This convention dates back to the early days of Unix, when it was developed as a text-based operating system. In Unix, files are stored as a sequence of lines, with each line terminated by a single LF character. This convention is also used in programming languages that were developed on Unix, such as C and its derivatives.

In contrast, in early versions of Microsoft Windows and MS-DOS, a carriage return (CR) followed by a line feed (LF) sequence is used to mark the end of a line of text. This convention goes back to the days of typewriters and teletype machines, which used both the CR and LF codes to signal the end of a line. When Microsoft developed its early operating systems, it inherited this convention.

The difference in line endings between Unix-like systems and Windows can cause issues when transferring files between systems. For example, if a text file created on a Windows machine is opened on a Unix system, the presence of the CR character may cause the lines to appear incorrectly. Similarly, if a text file created on a Unix system is opened on a Windows machine, the lack of the CR character may cause the lines to appear incorrectly.

To avoid these issues, many text editors and programming tools now have the ability to automatically convert line endings between Unix and Windows formats, or to handle both formats correctly.

我：Why is the end of the mac operating system a carriage return?

ChatGPT：Historically, Mac OS (now known as macOS) used a carriage return (CR) character to mark the end of a line of text. This convention dates back to the early days of the Macintosh computer, which was first introduced in 1984.

The Macintosh was designed to be a user-friendly computer that was accessible to non-technical users, and part of this design philosophy was reflected in the way it handled text. The original Macintosh operating system, known as System 1, used a simple, intuitive interface for editing text, which involved using the return key to create new lines of text.

To achieve this behavior, the Macintosh operating system used a single CR character to mark the end of each line of text. This was a departure from the convention used in other operating systems of the time, such as Unix and MS-DOS, which used a combination of a CR and a line feed (LF) character to mark the end of a line.

The use of a single CR character on the Macintosh made it easier for users to create and edit text, since they could simply press the return key to start a new line. However, this convention also made it difficult to exchange text files with other operating systems, which may expect a different line ending convention.

Today, macOS still uses a single CR character as the default line ending convention for text files created on the system. However, most modern text editors and programming tools are able to handle multiple line ending conventions, including the use of both CR and LF characters, to ensure compatibility with other operating systems.